The present invention is directed toward the field of heating ventilating and air conditioning (HVAC) controls and more specifically to the field of thermostats.
Thermostats are well known control devices used in controlling the operation of an HVAC system. Typically, residential dwellings have had one, two or occasionally three or more thermostats for the control of one or more HVAC systems in the dwelling. Usually, there was a one to one correspondence between the number of thermostats and the number of HVAC systems being controlled.
When there was more than one HVAC system and accordingly more than one thermostat in a dwelling, the plural thermostats operated in isolation of each other. In a two HVAC system house, one HVAC system might for example control the temperature on a first level while a second HVAC system may control the temperature on a second level.
A problem existed in that two HVAC systems and thermostats operated ignorant of what the other system and thermostat were doing. While one thermostat might notice at its temperature sensor some of the effects of the other HVAC system and thermostat operation, in general, by the time the temperature sensor notice the effects of the other system, a large deviation from the temperature setpoint could result.